Various types of braking systems are known. For example, hydraulic, pneumatic and electromechanical braking systems have been developed for different applications.
An aircraft presents unique operational and safety issues. As an example, uncommanded braking due to failure can be catastrophic to an aircraft during takeoff. On the other hand, it is desirable to have virtually fail-proof braking available when needed (e.g., during landing).
Furthermore, with respect to landing gear and braking systems, the environmental operating conditions may be severe. For example, these systems may be subjected to extreme and rapidly changing temperatures, for example, ranging between approximately −60° C. and 120° C. Such extreme temperature variations present difficulties in developing these systems.
In order to address such issues, various levels of redundancy have been introduced into aircraft brake control architectures. In the case of electromechanical braking systems, redundant powers sources, brake system controllers, electromechanical actuator controllers, and the like have been used in attempts to provide satisfactory braking, even in the event of a system failure.
In this regard, to effectuate braking, each wheel of the aircraft may be associated with multiple electromechanical brake actuators (EBAs) that each apply mechanical force to a brake stack associated with the wheel. Each EBA is driven with a drive signal that is generated specifically for that EBA. In these systems, high level brake commands are generated by one or more brake control units (BCUs), also referred to as a brake system control unit (BSCU). The signals from the BCU are converted into drive signals for each EBA by one or more electromechanical actuator controllers (EMACs). The EMACs consolidate control over EBAs in an area of the aircraft that is remote from the EBAs.
This architecture means that heavy gauge cables are used to carry high voltage drive signals from the EMACs to the EBAs, which can be a distance of fifty feet or more. The number of conductors can be very large (e.g., upward of about 60 conductors per wheel having four EBAs), leading to a significant amount of wire weight. The long drive distance creates significant series wire resistance, causing efficiency loss.
Further, the drive signals are modulated high-voltage power signals and are a source of significant electromagnetic interference (EMI) emission, particularly over the long drive distance the signals travel. Thus, the corresponding cables may be shielded to minimize their effect on other systems, though the shielding detrimentally results in additional weight.
Alternatively, the EMAC devices have been moved from the body of the aircraft to the landing gear. Though this embodiment benefits from wire weight reduction, it is still non-optimal, at least partially because EMI and electrical noise issues are still present. Additionally, the EMACs are large in size, which is generally viewed negatively by aircraft manufacturers and integrators. Furthermore, the extreme operating temperatures at the landing gear present design and operational difficulties.
Accordingly, a need exists for systems and methods for improved electromechanical braking for aircraft.